I need advice on how to use radcan



Hi all,

here is a simple example which frightens me:

(%i1) sqrt(a^2-2*a*b+b^2);
(%i2) radcan(%);
(%o2) b-a
(%i3) radexpand:false;
(%i4) radcan(%i1);
(%o4) b-a

I'm using:
Maxima version: 5.21.1
Maxima build date: 8:13 4/26/2010
Host type: i686-pc-mingw32
Lisp implementation type: GNU Common Lisp (GCL)
Lisp implementation version: GCL 2.6.8

I've used copy&paste to generate these expressions. Obviously, the 
mathematically correct answer would read abs(b-a) or abs(a-b). But at 
least, this behaviour of radcan() is documented.
But I firstly do not understand why "radexpand:false" does not work as 
documented and secondly, how I should proceed to simplify the 
expressions if I don't know (suppose a as well as b are complicated 
expressions depending on parameters) whether a<b or b<a, respectively.

Regards
Dragan